The seven-story-deep receiving pit where Bertha the SR 99 tunneling machine ended her years-long run has been transformed in just a matter of months as the Seattle highway project races toward the finish line.
A new video from the Washington State Department of Transportation captures work that has taken place between September 2017 and January 2018 to convert the deep hole in the ground near Seattle Center into the double-decker highway that runs through the completed tunnel.
Somebody on the multimedia team at WSDOT is also getting punchy in the waning months of creating this content, because the YouTube video is set to quite the little electronic dance ditty.
The 450-foot-long and 90-foot-deep pit was first excavated by crews back in 2013. It was a dusty, noisy scene for celebration on April 4, 2017, when Bertha busted through the final wall to end her 9,270-foot-long journey beneath the city. Crews have long since said bye bye to the hulking machine — another video back in August captured the disassembly of the 8,000-ton machine.
The new footage shows the lower northbound roadway going in first, followed by the upper southbound section of SR 99. Walls were then built to support the ceiling of that upper roadway. As more rebar and concrete is added, the pit continues to fill in and all of that infrastructure creeps toward street level.
A tunnel exit corridor is shown being added as well as ventilation ductwork and then giant girders are placed, spanning the old pit and providing support for a tunnel lid which will carry the weight of more north portal operations as well as part of Sixth Avenue North.
Track further progress on the tunnel project here. Traffic could be moving along the underground SR 99 as early as this fall.